Late-Season Soybean Management

Dan Davidson, Agronomist PhD, CPAg, CCA

Is late-season soybean management going to become the new reality – or do you just ride the crop to the end after R3?

Soybean management includes pre-planning, variety selection and placement, fertility, planting, weed control and crop protection. Generally, that takes us through R3 or pod set. But does late-season management after R3 still matter? Is there anything growers can do?

R3 reproductive management

Late-season management, in the minds of many growers, happens at the R3 reproductive stage. R3 begins when there is at least one pod that is 3/16 inch long at one of the four uppermost nodes of the soybean plant.

R3 is considered an ideal time to apply insecticides and/or fungicides to protect foliage and pods, providing about three weeks of protection that lasts well into R5/R6, where a second application is rarely justified.

Many of today’s growers strive for plant health by adding in foliar nutrients, growth regulators, growth enhancements (such as Fortalis®) or biologicals with plant protectant products at R3. This saves the cost of an extra pass across the field.

R4.5 late-season management

Late pod formation at R4.5, to early seed fill at R5.5, is a critical time for managing stress and resources. Yield reduction occurs mainly because there are fewer pods and seeds. Helping to prevent stress during late pod and early seed set can help to reduce yield losses.

  • R4 or full pod occurs when pods are ¾-inch long at one of the four uppermost nodes on the main stem.
  • R5 or beginning seed occurs when is seed is 1/8-inch long one at of the four uppermost nodes on the main stem.

Today’s soybean contest winners are adopting more late-season management strategies beginning at the R4.5 stage to reach 80, 90 or 100 bushels. They don’t want plants to be stressed or deprived of any resources including water, nutrients and light capture. They want to protect the foliage for as long as possible, maintaining plant health and a green canopy to feed those pod and seeds – minimizing the potential loss of either. Remember that any factors that impact yields can still limit yield if all other factors are optimal.

Any foliage loss during R4 and R5 will reduce yields. The plant can’t compensate as well if stress occurs. And stress will lower yields by reducing the number of pods per plant, beans per pod and even seed size. And at the end of the day, it’s seeds per acre that makes final yield.

If your yields aren’t increasing or reaching new heights, consider adopting some late-season practices to take your crop to the next level.

Fortalis® is an essential crop input

Your soybean yields can also benefit from Fortalis®, an advanced crop enhancement foliar spray that works by mobilizing calcium already existing within plant tissues, resulting in higher pod retention. When applied as a tank mix, Fortalis® with a fungicide or insecticide contributes to better plant health and higher yield potential. It’s an essential crop input that you need to get the most out of your crop.

Dan Davidson is a PhD agronomist, part-time farmer and soybean expert from Nebraska who consults with soybean checkoff and industry on crop production, marketing, and product development projects.

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